Spring for keeping pitmen off dead-centers



(No Model.)

, G A.'VAN ALLEN.

SPRING FOR KEEPING PITMEN OFF DEAD CENTERS.

No. 254,248. Patented Feb. 28,1882.

l WENT R- K UNITED STATES PATENT OFFICE.

CHARLES A. VAN ALLEN, OF CHICAGO, ILLINOIS, ASSIGNOR TO ROBERT K. SCOTT, OF NAPOLEON, OHIO.

SPRING FORKEEPING PIITMEN OFF DEAD-CENTERS.

SPECIFICATION forming part of Letters Patent-No. 254,248, dated February 28 1882.

' Application filed June 13, 1881. (No model.)

To all whom it may concern:

Be it known that I, CHARLES A. VAN AL- LEN, a citizen of the United States, residing at Chicago, county of Cook, and State of Illinois,'have invented a certain new and useful Spring for Keeping the Pitmen of Sewing- Machines Off of the Dead-Centers, of which the following is a specification.

My invention relates to an improvement in springs, and in the manner of attaching such springs to and operating them upon the pitman of a sewing-machine, so as to keep the pitman off of both its upper and lower center. The object of my invention is to avoid the necessity of starting by hand. the belt or fly wheel to set the machine in motion; to have the machine run with a continuous uniform motion-that is, without being subject to sudden or, violent jerks; and, finally, to enable the operation of the treadle by a toe-pressure alone, and by the exertion at" less power and with greater case than those now in common use. I attain these objects by a device illustrated in the accompanying drawings, in 2 5 whicht Figure 1 is a side elevation of my spring attached, and showing its position when the pit-.

man is on the upper dead-center; and Fig.2, a

dead-center.

Similar letters of referenceindicate the same parts in the figures of the drawings.

A represents the lower and larger coil of a wire spring removably clamped to a treadle 5 of a sewing machine intermediate the pivot of the treadle and the pivot of the pitman by ordinary, clamping-plates and a thumb screw, a projecting end of the coil being rigid- 1y secured to the upper plate. Contiguous with the spring A is an arm, 01, extending beyond the pitman and at an oblique angle to a horizontal plane, and having an eye, a, formed at its center of length by bending the wire. From the upper end of the arm a is a coiled spring, B, similar but smaller, and having its coils wound opposite to those of the spring A-that is to say, the arm passes from the bottom of the spring A to the top of spring B, as clearly shown in the drawings, so that the coils of the springs are necessarily wound similar view with the pitman on the lower in opposite directions relative to each other. The outer coil of spring B terminates in an oblique arm, I), which, crossing the arm a, terminates in an eye, 0, by means of which it is pivotally secured upon a lug or button upon 5 the clamping-plate, securing said arm to the pitmau, or by a lug upon thepitman.

As at present constructed the spring A consists of three coils, while the spring B consists of twocoils; but the number of coils or the relative size of them is surely optional and dependent upon the resistance of the crank and the size of wire used, and also the length of the arms a b, which, while operating as levers, have to a limited extent the function of springs.

To prevent the lower coil from contracting or overcoming the action of the upper coil during a certainportion of the stroke of the pitman, as will be presently described, hook-arm D, rigidly fixed upon the clamping plate, or else to the treadle, is connected by an adjustable chain, E, or other suitable device, to the eye a upon the arm a. V

In Fig. l the dotted line 1 3 indicates the 7 line of the dead-centers, while the dotted line 2 4 indicates opposite points exactly between the dead-centers.

To attach the spring the crank-arm is turned until on the line 2 4, (at which moment the springs and arms, if already attached, would be in their normal condition,) and having clamped the spring A to the treadle, making its pivot and the pivot of the crank, the arms a b are slightly spread, so that the spring may 8 not be loose, and arm I) is then clamped to the pitman.

It will be observed that the pit-manfls never vertical, but nearest it when the upper pivot is at 2, and farthest 011' when at 4; that when 0 at either of these points the arms a b, and consequently the springs A B, are in their normal condition; and that the dead-centers of the pitman are at one side or the other, as the case may be, of a vertical line, 5 6, drawn through 5 the axis of the belt or balance wheel. Furthermore, that when the upper pivot of the pitman is at 5 the arms a b are spread apart,the spring A expanded, and the spring B contracted to their utmost limits, and vice versa /I0O when the upper pivot of the pitman is at 6. Supposing the upper pivot of the pitman to be at 4, it will be understood that it a toepressure be exerted upon the treadle the pitman will descend and the arms of the springs be caused to approach each other until the upper pivot of the pitman is at 6, when they. begin to recede from each other.

Owing to the fact that the arm I) is shorter, and consequently more rigid, this movement has the effect of uncoiling and consequently expanding the spring B, and of lifting the arms a b, and hence contracting the spring A. As soon as the pivot of the pitman passes the vertical line 5 6 toward its lower dead-centers, and the arms commence spreadingapart. these springs exert themselves to resume their normal condition, and in doing so curr Y the pitman beyond the lower dead-center.

Under an ordinary toe-pressure, when starting the machine, the momentum of the balance-wheel is not suflicient to overcome the resistance of both springs, so as to carry the pivot of the pitman upwardly beyond the vertical line 5 6, though the toe-pressure is aug mented by the contraction and expansion of the springs as soon as the pivot of the pitman passes the line 5 6. To obviate this difficulty the chain E is used, which has the efi'ect of holding up the arm a and preventing the spring A from expanding during the time in which the pivot of the pitman is traveling from 2 to 4, the expansion of the contracted spring B, after passing the line 5 6, being alone sufiicient to throw the pitman off its deadcenters, when the toe-pressure may be again utilized.

Instead of a chain which admits of adjustabilty connecting the spring A with the eye a in the arm a, a hinged rodmay be used, and in some instances both may be; dispensed with and a lug be placed under to support the arm a, to prevent it from descending and the coil A from expanding.

Having thus described my invention, what I claim, and desire to secure by Letters Patent, 1s-

1. The combination, with a pitman and with its operating treadle, of a spring connected with said pitman and treadle, and adapted to throw the pitman off its dead-centers, substantially as described.

2. The combination, with a pitman and treadle, of an actuating-spring consisting of two or more coils, and adapted to simultanegusly contract and expand, for the purpose set orth.

3. The combination, with a pitman and treadle, of a spring having two or more coils simultaneously expanding and contracting, and a tension chain or cord connected with and adapted to limit the expansion of one of said springs.

4. In a sewingmachine, the combination, with the pitman and treadle, of a spring consisting of the coils A B, an arm, a, connecting said coils, and an arm, 1), connecting the coil B with the pitman.

5. The combination, with the coils A B and arms a 1), connecting said coils with each other and with the pitman and trcadle, of an arm, D, and a tension chain or cord connecting the arm a, with the arm D, substantially as and for the purpose set forth.

CHARLES A. VAN ALLEN.

Witnesses:

J NO. G. ELLIOTT, W. O. WHITING. 

